Injection molding machine screw is a long time in the high temperature, high pressure, high mechanical torque and high friction environment to work. The first few factors are required for the process conditions and the friction losses are inevitable. General screw surface nitriding have been carried out to improve the surface hardness, that is, to improve anti-wear ability. However, if you neglect the cause of wear and tear, try not to minimize wear and tear, is bound to greatly reduce the service life of the screw.
The following describes the cause of wear and tear caused by the screw and reduce the method:
1, Each plastic has an ideal plasticizing processing temperature range, it should control the barrel processing temperature, make it close to this temperature range. Granular plastic into the barrel from the hopper, will first reach the feeding section, the feeding section will inevitably appear dry friction, when these plastics lack of heating, uneven melting, it is likely to cause the cylinder wall and screw surface wear increased. Similarly, in the compression section and the homogenization section, if the molten state of the plastic is not uniform, the abrasion may also be increased.
2, speed should be properly adjusted. As part of the plastic with toughening agents, such as fiberglass, minerals or other fillers. The friction of these materials on metallic materials is often much greater than that of molten plastic. Injection of these plastics at high rotational speeds will increase the shearing force on the plastic and at the same time will result in more shredded fibers correspondingly to the reinforcement. The shredded fibers will have sharp ends that will cause wear The power is greatly increased. Inorganic minerals in high-speed sliding metal surface, the scraping effect is not small. Therefore, the speed should not be adjusted too high.
3, to check the debris in plastic. Generally speaking, the fresh plastic purchased originally has no debris. However, it may be mixed with debris after being transported, weighed, dried and mixed, especially when adding recycled materials. Small, such as the end of the metal shavings, as large as the heating ring nut paper clip, or even a string of warehouse keys, have been mixed into the barrel have occurred, which is self-destructive screw damage (and of course the barrel will also damage ), It must be installed magnet holder, rigorous feeding management and monitoring.
4, the water contained in the plastic, the wear and tear on the screw surface has a certain impact. If the plastic does not exclude all the water before injection, the residual moisture enters the compression section of the screw and forms a "steam particle" with high temperature pressure before melt blending in the molten plastic. With the progress of the screw in the injection process, The section until the screw head, these "steam particles" in the process of shooting the pressure relief expansion, like a tiny particles of hard impurities, friction damage to the wall. In addition, for some types of plastics, at elevated temperatures and pressures, moisture can become a catalyst for plastic cracking, creating harmful impurities that can attack metal surfaces. Therefore, the plastic injection molding drying work, not only the quality of the workpiece has a direct relationship, but also affect the working life of the screw.
